Potentiometric titration of tellurium with a fluoride-selective electrode

Tellurium, as tellurite, can be determined with a fluoride-selective electrode by means of an indirect procedure based on precipitation of tellurite with excess of lanthanum(III), followed by back-titration with standard fluoride. The end-point is located by using the Gran method, and the titrations are suitable for tellurite concentrations above 1 mM.     

Potentiometric determination of hydrogen peroxide at MnO2-doped carbon paste electrode

A novel hydrogen peroxide (H₂O₂) potentiometric sensor, made with a MnO₂-doped carbon paste electrode (CPE), is reported. Under optimum conditions, the electrode gives a Nernstian response for H₂O₂ in the concentration range 3.00×10⁻⁷–3.63×10⁻⁴ mol/l, with a slope of 21–19.4 mV/pH₂O₂ and a detection limit of 1.2×10⁻⁷mol/l H₂O₂. In addition, this sensor offers some analytical characteristics such as sensitivity, good reproducibility and a simple preparation procedure. The effects of both the components of the electrode and other conditions on the potential response of the sensor, as well as the possible response mechanism, are discussed.     

Electrodeposition of milligram amounts of uranium on electropolished stainless steel disks

Investigations have been carried out for the electrodeposition of milligram amounts of uranium on electropolished stainless steel disks with an objective of preparing good quality sources for -spectrometric studies on uranium. The parameters studied include the variation of electrodeposition yield as a function of voltage, time, distance between the cathode and anode, and the volume of 0.2M ammonium oxalate solution. The conditions selected for preparing good quality sources with nearly 100% yield were: electrodeposition voltage 25 V, time of deposition 15 min, volume of 0.2M ammonium oxalate solution in the cell 4 ml and a distance of 2 cm between the cathode and anode. The sources prepared using this method have been used successfully for the -spectrometric determination of²³⁴U/²³⁸U ratios in uranium samples.     

Potentiometric titration of sorbed hydrogen on palladium carrier catalysts

A method of determination of adsorbed and absorbed hydrogen on palladium catalysts with carbon carriers is suggested and verified. The method allows H_ad and H_ab to be determined with an accuracy of about 10% using catalysts containing at least 5% Pd.

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- . . . 10% , , - , 5% Pd.

     

Non-enzymatic hydrogen peroxide sensor using an electrode modified with iron pentacyanonitrosylferrate nanoparticles

An electrochemical sensor was developed for determination of hydrogen peroxide (HP) based on a carbon ceramic electrode modified with iron pentacyanonitrosylferrate (FePCNF). The surface of an iron-doped CCE was derivatized in a solution of PCNF by cycling the electrode potential between ?0.2 and +1.3 V for about 60 times. The morphology and the composition of the resulting electrode were characterized by scanning electron microscopy and Fourier transform infrared techniques. The electrode displayed excellent response to the electro-oxidation of HP which is linearly related to its concentration in the range from 0.5 μM to 1300 μM. The detection limit is 0.4 μM, and the sensitivity is 849 A M ^?1?cm ^?2. The modified electrode was used to determination of HP in hair coloring creams as real samples.     

Potentiometric coulometry based on charge accumulation with a peroxidase/osmium polymer-immobilized electrode for sensitive determination of hydrogen peroxide

The charge accumulation due to peroxidase (POD)-catalyzed reduction of H₂O₂ in a test solution (4 μL) by Os(II) in a POD/PVI[Os(dmebpy)₂Cl]-immobilized layer on an electrode (PVI = poly(1-vinylimidazole), dmebpy = 4,4′-dimethyl-2,2′-bipyridine) was monitored potentiometrically for the detection of H₂O₂. Before potentiometry, the Os(II)/Os(III) ratio of the modified electrode was controlled by pre-electrolysis at a given potential in a separated electrolysis cell. The redox potential of the Os polymer film in the test solution shifted to the positive side on the addition of H₂O₂ and reached a constant value due to the accumulation of Os(III) in the film. The total amount of the accumulated charge was determined from the area of the portion corresponding to the redox potential shift on a reversible cyclic voltammogram recorded separately. The low detection limit (5 pmol H₂O₂) was realized with 82–90% of the recovery percentage.     

Potentiometric titration of cyanide and chloride, using the silver specific-ion electrode as an indicator

Conditions are given for consecutive potentiometric titration of cyanide and chloride in mmole amounts, a silver-specific electrode being used as indicator electrode.     

Potentiometric titration of cyanide using the cation-sensitive glass electrode as indicator

Summary The argentometric determination of cyanide was re-examined in order to compare the cation-sensitive glass electrode and the silver metal electrode as indicator electrodes for this titration. Contrary to earlier reports, the glass electrode is capable of indicating both titration end points and yields stoichiometric information comparable to or better than that obtained with the silver metal electrode. In the presence of redox interferences, the glass electrode is superior to the silver metal electrode for titration purposes.

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Zusammenfassung Die argentometrische Cyanidbestimmung wurde im Hinblick auf einen Vergleich der kation-empfindlichen Glaselektrode und der Silberelektrode als Indicatorelektroden nochmals untersucht. Im Gegensatz zu früheren Berichten ergab sich, daß die Glaselektrode beide Endpunkte der Titration anzeigen kann und Aussagen über die Stöchiometrie gestattet, die vergleichbar oder besser sind als die mit Hilfe der Silberlektrode erhaltenen. In Gegenwart von Oxydations- oder Reduktionsmitteln erweist sich die Glaselektrode als besser geeignet.

     

Potentiometric microdetermination of arsenic with an iodide-selective electrode

Summary Micro amounts of arsenic(III) can be determined potentiometrically by titration with cerium(IV) sulphate at pH 2 with iodide as catalyst. An iodide-selective electrode is used to follow changes in the iodide concentration during the titration. Arsenic(III) at a concentration of 0.1g/ml can be determined with a relative standard deviation of about 5%. Total arsenic can also be determined with an error of 10–12%, the arsenic(V) being reduced with sodium bisulphite to arsenic(III). Direct determination of not less than 100 ng/ml of arsenic(III) in the presence of an unspecified amount of arsenic(V) and up to a fiftyfold ratio of iron(II), sulphide, thiosulphate, tin(II) and antimony(III) is possible.

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Potentiometrische Mikrobestimmung von Arsen mit einer jodidspezifischen Elektrode

Zusammenfassung Mikromengen Arsen(III) können potentiometrisch mit Cer(IV)-sulfat bei pH 2 mit Jodid als Katalysator bestimmt werden. Eine jodid-spezifische Elektrode dient zur Kontrolle der Jodid-Konzentrations-Veränderungen während der Titration. Arsen(III) Iäßt sich in einer Konzentration von 0,1g/ml mit einer rel. Standardabweichung von 5% bestimmen. Das Gesamt-Arsen kann ebenfalls mit einem Fehler von 10–12% bestimmt werden, nachdem Arsen(V) mit Natriumsulfit zu Arsen(III) reduziert wurde. Die unmittelbare Bestimmung von wenigstens 100 ng/ml Arsen(III) in Gegenwart einer unbestimmten Menge von Arsen(V) und bis zu einer 50-fachen Menge Fe(II), Sulfid, Thiosulfat, Sn(II) und Antimon (III) ist möglich.

     

Hydrogen peroxide sensor based on a stainless steel electrode coated with multi-walled carbon nanotubes modified with magnetite nanoparticles

Multi-walled carbon nanotubes (MWCNTs) were decorated with magnetite (Fe₃O₄) nanoparticles and then used to modify a stainless steel electrode. The Fe₃O₄/MWCNTs composite was characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction patterns. Electrochemical properties of the modified electrode revealed a substantial catalytic activity for the reduction of hydrogen peroxide. The relationship between peak current and the concentration of hydrogen peroxide was linear in the range from 0.06?mmol?L^?1 to 0.36?mmol?L^?1, and the lowest detectable concentration is 0.01?mmol·L^?1 (S/N?=?3). The modified stainless steel electrode displays excellent stability.

Potentiometric titration of organic cations with sodium tetraphenylborate and a liquid-membrane tetraphenylborate ion-selective electrode

Simple potentiometric titrations are described for the determination of various organic cations (usually 5–25 μ mol) with 0.01 M sodium tetraphenylborate. A liquid-membrane electrode with tetrapentylammonium tetraphenyiborate dissolved in 4-nitro-m-xylene as liquid ion-exchanger is used successfully in the semi-automatic titration of quaternary ammonium compounds, cationic surfactants, alkaloids and other substances of pharmaceutical importance which are precipitated by tetraphenyiborate. Analysis of pharmaceutical preparations gave satisfactory results.     

Potentiometric titration of plutonium

In the potentiometric titration of plutonium(III), it has been customary to take the equivalence point as the inflection point on a plot of potential vs. volume of titrant.¹ That the stoichiometric end point corresponds to the inflection point does not seem to have been theoretically demonstrated, however. The purpose of this letter is to suggest that these points may not correspond in the potentiometric titration of plutonium(III). Mound Laboratory is operated by Monsanto Research Corporation for USERDA under contract No. EY-76-C-04-0053.     

Potentiometric titration of permanganate with resacetophenone oxime

Milligram amounts of permanganate can be titrated with resacetophenone oxime (4-acetylresorcinol oxime) as a reducing titrant in the presence of phosphoric acid (0.5 M). The stoichiometry between permanganate and the oxime is 3:1 (MnO₄^-:oxime). The titration is successful in the presence of large amounts of dichromate or vanadate or moderate amounts of cerium(IV).     

Potentiometric determination of boron in silicon with an ion-selective electrode

A potentiometric method is proposed for the determination or boron in silicon, based on dissolution of silicon by treatment with hydrofluoric acid and ammonium fluoride in the presence of hydrogen peroxide, and conversion of boron to fluoroborate ion. The fluoroborate activity is measured with the Orion fluoroborate-selective electrode. Some important points, such as the effect of various interfering ions and the hydrolysis of fluoroborate ion, are described in detail. The method is applied to the determination of boron in silicon containing at least 10 p.p.m. of boron, with a relative standard deviation of ±4%.     

Potentiometric titration of lignosulfonic acids

The conditions of potentiometric titration of lignosulfonic acids allowing quantitative determination of strongly and weakly acidic functional groups in lignosulfonates were determined.     

Potentiometric titration of diprotic systems

 The approximate nature of Gran’s method of linearization of potentiometric titration curves applied to diprotic systems has been thoroughly investigated. A function involving pH and titrant volume V (which is linearly dependent on V and becomes zero at the first equivalent point of titration of a weak diprotic base with a strong monoprotic acid) has been critically examined and validated by means of widely extended simulated experiments. Accurate experimental confirmation of the theoretical expressions has been obtained by performing many real titrations of the primary standard Na₂CO₃ with HCl. This particular application, analytically significant itself, can be a prototype of analogous applications. Received: 25 March 1996/Revised: 15 November 1996/Accepted: 19 November 1996     

Potentiometric titration of diprotic systems

 The approximate nature of Gran’s method of linearization of potentiometric titration curves applied to diprotic systems has been thoroughly investigated. A function involving pH and titrant volume V (which is linearly dependent on V and becomes zero at the first equivalent point of titration of a weak diprotic base with a strong monoprotic acid) has been critically examined and validated by means of widely extended simulated experiments. Accurate experimental confirmation of the theoretical expressions has been obtained by performing many real titrations of the primary standard Na₂CO₃ with HCl. This particular application, analytically significant itself, can be a prototype of analogous applications. Received: 25 March 1996/Revised: 15 November 1996/Accepted: 19 November 1996     

Potentiometric titrations in non-conducting solutions with an interfacial antimony electrode

The micro interfacial device described is based on an antimony/antimony scratch/ 0.1 M KCl/Hg₂Cl₂/Pt cell. Acid—base reactions occurring in solvents such as dry ligroin, benzene, cyclohexane, dichloroethane, chloroform and pentyl acetate are readily monitored.     

Potentiometric titration of sulphate, sulphite and dithionate mixtures, with use of a lead ion-selective electrode

Simple methods are described for the analysis of sulphate, sulphite and dithionate mixtures by potentiometric titration with lead perchlorate (and use of a lead ion-selective electrode). The error and precision are both about 2–5% for the sulphate concentration range 3 × 10⁻³ −6 × 10⁻⁴M. The sulphur content in fuels derived from refuse was determined by potentiometric titration after bomb-combustion and the results compared favourably with those from the standard BaSO₄ gravimetric method.